A good night's sleep is one of the most important things to do for health. Whether weight loss, mental health or beauty is the goal, catching ZZZs is key. In fact, anyone who's beauty obsessed already knows sleep is a critical time for refreshing and renewing. But what *actually* factors into a good night's sleep? What you eat, when you hit the sack and physical activity can all play a part in securing beauty sleep, but so can your mattress. In fact, you might not always think of it, but the quality of your bed itself can impact the quality of your sleep. We're taking a look at what happens when you get beauty sleep and how you can change your environment to make the most out of your night.

When the lights go out

When our bodies hit the sack, a lot happens. "It's important that people get a good night's sleep because that's when skin is best able to repair itself and oxygenate itself from the day," explains Dr. Rebecca Kazin, Medical Director of the Johns Hopkins Dermatology and Cosmetic Center. In essence, sleep isn't just a time for dreams. It's the time in which our skin, which also follows a circadian rhythm similar to our sleep pattern, can rehydrate and refresh.

This is also when our bodies produce growth hormones. Dr. William Christopher Winter, a board-certified and nationally recognized sleep medicine doctor as well as a board-certified neurologist, explains growth hormones are only produced during deep sleep for adults and are critical for the body's daily recovery, injury recovery, immune system functioning and overall vitality.

During this stage of delta sleep, true physical restoration occurs, says Dr. Michael Breus, clinical psychologist and author of Beauty Sleep: Look Younger, Lose Weight, and Feel Great Through Better Sleep, through not only growth hormone secretion but cellular repair as well. Cellular repair is responsible for repairing all the minor damage the skin and body have received throughout the day.

But if you're sleep deprived, less growth hormone is produced, cellular repair and metabolism slows down and blood circulation even decreases, causing pooled blood a.k.a. dark circles and high blood pressure, which leads to puffiness. Not to mention skin's overall rosy appearance disappears.

"When you have lowered circulation, nutrients are not going to you hair, skin, nails," explains Dr. Breus. Basically, your body is not making those necessary maintenance repairs.

The wrong side of the bed

There is a wrong side of the bed, as anyone who missed a few hours of shut eye will attest. When we get a bad night's sleep, it shows—and we don't just mean with dark circles.

In fact, in a Swedish study, 23 adults were photographed on a full night's sleep (eight hours) and again after only five hours. Observers were asked to look at the two photos and rate in which photo the subject looked more healthy and more attractive. The majority of the observers rated the photo taken after eight hours of sleep as more attractive and lively than the more sleep deprived one.

But beauty isn't just physical; it's emotional. And to no surprise, there's an emotional side of sleeping.

"If you're sleep deprived, there's a greater likelihood any emotional scenario you have is going to be worse," explains Dr. Breus. "So if you're a normal healthy person, the more sleep deprived you are the more likely you are to add valence to emotions. Jokes might seem funnier, but you might be more offended by things."

So in theory, getting a good night's sleep can have an effect on our general mood, thus possibly making us more enthusiastic about our physical appearance. Ever wake up inspired to attempt that fabulous smoky eye? Guess there's a reason behind that saying "bright-eyed and bushy tailed."

Creating the ideal bedtime

If there's ever one time it's okay to play Goldilocks, it's when you sleep. Sleeping in a room that's too hot or too cold is like showing up to a marathon without training — it just doesn't work. To get the most comfortable sleeping environment, Dr. Winter says opt for a room temperature of the mid 60s to help lower the body temperature.

But besides setting the thermostat, giving yourself enough time for sleep is key to the body's repair cycle. We've all heard that eight is a magic number, but really, there's no set number of hours we're required to get each night. According to Dr. Winter, much like caloric need, the amount of sleep needed is really dependent on each individual person.

"The idea of saying a number [of hours of sleep you should get] is difficult because you'll have people who will really do best with seven hours of sleep," says Dr. Winter. "But if you tell them eight hours is better, it can really backfire if they're trying to get eight, and they can't. Then they'll start to struggle with what they would consider to be insomnia."

Similar to the time spent asleep, the position in which you sleep can also effect your appearance. Constantly sleeping in the same position on your side or your stomach can cause permanent creases in the skin, says Dr. Kazin. She also explains side or belly sleepers who drool when they sleep can breakout or get heat rash in that area.

So what is the ideal sleeping position for all-around health?

"The best position for sleep is actually on your back," says Dr. Breus, "Because the weight is displaced across the skeletal plane with the largest amount of surface area that way. When you sleep on your side, everything kind of falls to the side that you're sleeping on. So from a gravitational perspective, you're crushing all the capillaries of the side that you're sleeping on."

Although we have little control on how we end up sleeping throughout the night—some of us twist and turn and end up at the foot of the bed even — those who sleep on their backs benefit the most when it comes to beauty as there's no pressure on the face, breasts or other parts of the body. So if you can help it, back sleeping à la Sleeping Beauty is key. Gown and crown optional.

What about the mattress?

Now that you know why a good night's sleep is essential for all things beauty related, how does one get a truly restful night? Besides turning off technology at night — yes, step away from Snapchat — finding a bed that will actually create a sanctuary is equally important.

"I believe sleep is a performance activity," says Dr. Breus. "If you have the right equipment, it's going to be helpful in the level of performance." He explains the biggest function of a mattress is supporting the spine, the head and the neck in a way shape and form that's comfortable, neutral and allows the body to regenerate in the evening. The problem is there's no one mattress that can do this for everyone.

"The ideal mattress is the mattress that you sleep best on," says Neil Parikh, Co-Founder & Chief Operating Officer of Casper. [Ed note: Several MIMI editors have the Casper mattress and are ob-sessed with it.] Because there's not one bed to suit everyone, it's important to take into consideration what your sleeping needs are.

Parikh says a top complaint from consumers when it comes to mattresses is heat retention — a factor the Casper brand took into account when creating their mattresses. "There are two main reasons why people sleep hot," says Parikh of current memory foam options. "Most memory foam isn't very breathable, and the material tightly conforms to your body, so there isn't enough air space around your skin. When your body is enveloped in a non-breathable memory foam, the material gets toasty, and you get sweaty." Bottom line: if you're prone to getting hot, perhaps memory foam isn't for you.

Another factor to consider is your partner. If you share your bed, consider a latex mattress. As Dr. Winter points out, latex is a natural material, which is hypoallergenic, resistant to bacteria, mildew, mold and dust mites. But it's also highly customizable on each side thanks to its pliable nature. Most importantly, it's very easy to replace if you decide you want a different firmness over time. Or if your bed partner changes.

Whether you're looking for a spring, air, water or foam mattress, "to each his or her own" is a good rule of thumb. Just make sure to fully test the bed before buying. Dr. Breus suggests going mattress shopping at the end of the day when your body is most tired, wearing lose clothing, taking off your shoes, bringing your own pillow and making sure to lie on each side you sleep on for at least 15 minutes to get the most out of your shopping experience.

At the end of the day, our experts all agree there was no hard and fast rule to sleeping. Just make sure you equip yourself with the gear you find the comfiest and let your body to the rest.